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Old 10-15-2009, 11:11 AM   #1
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Shed questions


As I continue with my shed... I included a picture of what I'm going to do if it helps. Again, I don't want a subpanel the shed is too tiny I just want light mostly but including a recept inside it just in case there's also going to be a recept on the house close by.

Here are the rules as I understand, please correct me if I'm wrong.

1.) Sheds require a kill switch (whether it be a subpanel or light switch if 20A or less) before going to any recepts, lights, etc. of said shed. I planned on using a regular light switch since this will be 20A and get a red cover but I don't think I can wanting a 3-way. More later.

2.) With the circuit being protected upstream by GFCI I need to bury the conduit 12" minimum. I plan on going 24" if possible and using 1" grey pvc and sealing all joints with the grey pvc electrical glue.

3.) This is considered a utility area (like ones unfinished basement) and as such the wires inside the shed do not need to be in conduit or armored.

For a question, I have no idea how to do that 3-way light switch the way I want (inside by the door AND controlled outside at the shed). Should I run a couple 12/2 THWN? Do they make a single 12 gauge THWN for wet locations I can use for common? What kind of kill switch will I need cause I'm no 3-way light expert but don't I need to handle the killing of both the black & common seperately with one switch?

Thanks
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Old 10-15-2009, 11:22 AM   #2
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Instead of single circuit I would run a MWBC (multi-wire branch circuit)
This is 2 circuits fed by a 240v breaker for 2 hots that share a neutral
Bury at 18" instead

Not sure on the 3-way switch wiring from the house & the shed

Where are you located? Codes due vary by area
Wires do need to be protected from physical damage, usually running in the stud cavity takes care of this

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Old 10-15-2009, 01:47 PM   #3
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Well, the problem with an MWBC is all my breakers are full and I didn't mention the shed is tiny. I really want the floodlight and figure I might as well wire it and put a light inside (and add a recept).

I don't have anything covering the stud cavities if that's okay, it' so small covering them would take away my space. I decided I'm going to run the wires inside the shed in conduit, it's cheap enough and moving stuff in/out I might wack the wire(s) so better to protect it even if I don't have to.

That 3-way the way I want has me baffled as well, if they made THWN in 12-3 (White, Black, Red, Ground) I'd be set (maybe they do). Or, maybe they make it in 12-2 and sell a single red THWN I can use. I really don't know what's out there for THWN and hope experts chime in with what's available or how they'd do it.

I'm thinking the shed needs a double-pole single throw for the kill switch (one side handles the common of the 3-way, the other the black for the entire shed). One flick and everything should be killed. I won't be living in this house for many more years so I don't want to go too crazy with this but can't go one more year without the floodlight and I need it before it snows (coming soon I'm sure!!!).

Thanks

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Old 10-15-2009, 02:14 PM   #4
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Looks like you have a good plan with a 3/4 pvc pipe you can run 16 #12 wires just make sure you mark your 3 ways and withe your gfci on the main building the pipe you put in the ground only has to be 12 inches
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Old 10-15-2009, 02:19 PM   #5
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You should be able to buy 12-3 UF for direct burial, you can put it in conduit if the pipe is big enough
Or if you want conduit & single wires just buy the lengths/colors you need of THWN
Connect it just like a 3 way
On the shed have a double throw that kills both red & black
But - if that switch is off the 3 way from the house will not turn the spotlight on
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Old 10-20-2009, 10:23 AM   #6
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I just want to update you folks as to how this went.

I did end up putting three 45's running the conduit, I hit rocks the size of VW bugs and had to go around them. Had A LOT of trouble pulling two lines of 12-2 UF-B ($63) through 3/4" conduit. My wire puller broke within the first 5 feet trying to pull it it was that hard. Just one slow turn 90 and a 45 was extremely difficult. I ended up having to build the conduit as I went. I got all the way to within 1' of finishing and the wire jammed, the harder I pulled the worse it got. I cut the conduit and the jam in the UF-B and still had enough wire for the run to try again. Within 1' of finishing again one of the wires knotted, I didn't have enough to cut the knot out and have enough for the run, nor could I push it back. So I failed trying to run 2 lines of 12-2 UF-B through 3/4" conduit. I cut the the conduit and UF-B out.

Next day I paid $73 for 5 lines of #12 stranded THWN and some couplings and the stranded THWN went through the conduit like butter. I think pushing it the entire run was easier than trying to move the 2 lines of 12-2 one inch! I tell my wife it's over, and she tells me "Awesome! Oh, I meant to tell you I changed my mind about the 3-way I just want it on sensor. You don't need to run the extra wire for the 3-way". I kept my cool... but I was thinking $120 extra and 6 hours of work too late now!

So, I have 5 lines (2 extra) and I'm done. I guess I'll double-up the white & black with the extra lines so there's less resistance for the time being and if the next person wants to do something they have 2 extra wires. Lesson learned... use stranded THWN instead of UF-B in conduit, even one line of 12-2 UF-B is very difficult

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Old 10-20-2009, 10:40 AM   #7
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I guess I'll double-up the white & black with the extra lines so there's less resistance for the time being and if the next person wants to do something they have 2 extra wires.
Nope. Can't do that for small conductors like these. Just put wire caps on all ends and mark where they are going.
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Old 10-20-2009, 10:43 AM   #8
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Yeah, I've only pulled NMB thru about a 12" sleeve
Did you use any wire lube at all?
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Old 10-20-2009, 01:31 PM   #9
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Lesson learned... use stranded THWN instead of UF-B in conduit, even one line of 12-2 UF-B is very difficult
I am absolutely appalled that someone did not warn you about pulling cable into conduit. Sorry you had to learn the hard way.
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Old 10-20-2009, 02:48 PM   #10
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Did you use any wire lube at all?
Hmm... that probably would've been useful I've not heard of it.

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Nope. Can't do that for small conductors like these. Just put wire caps on all ends and mark where they are going.
Intersting, do you know why? I can see the reason if this were a 30 amp circuit and someone tried to double-up #12s instead of running a #10... if one of those #12s failed you'd be left with 30 amps possibly flowing through a #12... not good! But this circuit is on the same 20A breaker.

I'm having trouble understanding why at the outdoor recept on my house since I have 4 lines + ground running to my shed I can have my lights & recepts on different wires (but all fed from the same circuit from the breaker panel) as long as it's on the house and that's okay. But I can't double them up to the shed and do it from the sheds recept... I personally think it's the same thing.

Last edited by Piedmont; 10-20-2009 at 03:16 PM.
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Old 10-20-2009, 03:01 PM   #11
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NEC 310.4(A) only permits conductors over 1/0 size to be run in parallel like your #12s, with a few exceptions (which don't apply to you).

I think you hit the nail on the head - to prevent what you described about raising the circuit and breaker ratings because you have parallel conductors.
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Old 10-20-2009, 03:52 PM   #12
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Interesting, it doesn't sound like they're taking the breaker into consideration. It's funny on a 20A breaker I can run 6-2 if I wanted, or 12-2... but I can't run two 12-2 in parallel to lower resistance.

Well then, to help offset the load I have 4 wires + ground running to my shed and I will then have the lights hooked into one set and the recepts hooked into the other. It's not as good to me as letting me run them in parallel but does help with lower resistance (I think) and give my 2 other wires some use. I drew a diagram of what's okay and what's not.

I think I hit something like this with grounding my outdoor antenna. They require it be grounded to a grounding rod below and requires the antenna to the grounding rod to be #10 or better. However, some other rule requires all grounding rods be bonded to the breaker panel with #6 I believe. It's funny seeing I need only #10 to the grounding rod and that's okay but need a whopping #6 from it to the breaker panel.

Thank you, I like things be done right and glad you mentioned something
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Old 10-20-2009, 09:06 PM   #13
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Well then, to help offset the load I have 4 wires + ground running to my shed and I will then have the lights hooked into one set and the recepts hooked into the other. It's not as good to me as letting me run them in parallel but does help with lower resistance (I think) and give my 2 other wires some use. I drew a diagram of what's okay and what's not.
I have to agree, it doesn't seem right that you can double tap a breaker, run it to 2 different circuits, but you can't run the two wires in parallel to the same circuit.

Maybe I'm screwed up...that's always possible...

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